The mystery of the ‘ghost frequency’, the most terrifying sound known to man

In the early 1980s, Vic Tandy was one of a team designing medical equipment in a laboratory at Coventry University. Everybody said that the lab was haunted; it just felt weird in there. That evening, when Tandy was on his own, he felt something very strange. 

“I was sweating but cold, and the feeling of depression was noticeable – but there was also something else,” he told the Birmingham Post at the time. Suddenly, he felt like he was being watched. “It was as though something was in the room with me.” 

A greyish shape appeared on the edge of his vision. The temperature dropped. As he turned to look at the shape, it disappeared. “There was absolutely no evidence to support what he had seen so he decided he must be cracking up and went home,” Tandy and his colleague Tony Lawrence wrote in a 1998 paper on the incident.

Tandy was a man with many interests. He became a lecturer in information technology at Coventry University and was an engineer, but was also a keen magician and member of the Leamington and Warwick Magic Society. In his spare time he had time to go fencing too. On another evening in the same laboratory, another odd thing happened. 

His fencing foil was clamped in a vice on a table in the middle of the room. Nothing else was touching it but slowly at first, then faster and faster, the blade started to vibrate up and down. Intrigued, Tandy started to investigate and discovered a new extractor fan near the laboratory. It was sending rumbling, low-frequency soundwaves of 18.9 hertz into the laboratory, which were bouncing around and focusing where his foil was clamped. 

These frequencies were below the range that the human ear can hear, but Tandy surmised that these low-frequency sounds – known as infrasound, the polar opposite to high-frequency, high-pitched ultrasound – were what had caused his experiences. In another investigation a few years later, Tandy found that an apparently haunted 14th century cellar underneath Coventry’s tourist information centre was focusing infrasound at 19 hertz from the pump of a nearby fountain. 

“To find exactly the predicted frequency was astonishing and the experiment was repeated several times to ensure that it was not an anomaly of the equipment. While reluctant to rule out other frequencies in the infrasound band, clearly 19 Hz must be of particular interest,” he wrote in a 2002 paper titled Something in the Cellar.

Tandy and Lawrence suggested that frequencies of 19 hertz – invisible, inaudible waves which seep through buildings and the ground, and into our bodies – might caused those exposed to experience what they perceive as a haunting. Since their work the so-called “ghost frequency” has built up quite a mythos: some say it can make you vomit, send you running from a room, or induce shivers and sweat. 

The paper even suggested it could make you see ghosts, citing a Nasa report that put the resonant frequency of the human eyeball at 18 hertz. “If this were the case then the eyeball would be vibrating which would cause a serious ‘smearing’ of vision,” Tandy and Lawrence’s first paper, Ghost in the Machine, put it in 1998. “It would not seem unreasonable to see dark shadowy forms caused by something as innocent as the corner of [Tandy’s] spectacles.”

But that’s not all infrasound can reputedly do. In 2003, director Gaspar Noé admitted adding low frequencies to scenes in his film Irréversible to unsettle audiences. “You can’t hear it, but it makes you shake. In a good theatre with a subwoofer, you may be more scared by the sound than by what’s happening on the screen. A lot of people can take the images but not the sound. Those reactions are physical.” 

Some cinemagoers on Reddit recalled feeling nauseous and unnerved while watching Irréversible, though that might have been down to graphic sequences where characters are sexually assaulted or beaten to death with fire extinguishers rather than any “fear frequency”. Yet Noé isn’t alone in using deep frequencies to try to scare audiences: Paranormal Activity and The Conjuring 2 are rumoured to have used infrasound, as was the zombie movie The Battery. How, though, does infrasound work?

Human speech spans between around 500 and 2000 hertz, and the lowest C note on an 88-key piano is just under 33 hertz. Infrasound, explains Dr Trevor Cox, head of acoustics research at Salford University, is generally taken to be anything below 20 hertz. Noé added 27 hertz to Irréversible, so technically it isn’t infrasound. “But the key thing from a perception point of view is your ear can still pick this up. It just has to be very loud for it to be audible.”

All sorts of things create infrasound in our everyday lives: big engines and fans, washing machines, thunderstorms. Tandy wasn’t the first person to investigate infrasound: the Moscow-born scientist Vladimir Gavreau’s experiments in the 1960s led him to suggest that the Soviet Union created a giant 10,000 watt acoustic resonator to kill enemies with silent sound. “There is one snag,” William S Boroughs noted in a 1968 National Enquirer article about it. “At present, the machine is as dangerous to its operators as to the enemy.”

Not everybody is sensitive to infrasound. Whether you are or not is due in part to how good your hearing is, and partly a natural sensitivity. “So some people can hear it, some people can’t, and that’s just natural variation.”

Tandy died suddenly in 2005, aged 50. But two papers he and collaborator Tony Lawrence published in 1998 and 2003 theorising that infrasound might explain reports of hauntings have lived on as other academics have investigated too. Ciàran O’Keeffe, a parapsychologist and head of the School of Human and Social Sciences at Buckinghamshire New University, is one. You’ve felt sound affect your body before, he says.

“Imagine you’re in a club and there’s a very deep, deep bass playing through the speakers and you’re relatively close to the speakers,” says O’Keeffe. “And you can hear the beat, but actually you can feel it in the pit of your stomach.” 

Add in infrasound frequencies and there are other effects too. “There can be kind of a heaviness, on your head or your ears. Some people even report hairs going up on the back of their neck, a sense of presence as well.”

Sarah Angliss is a composer and sound designer who has used infrasound in theatre productions, and whose background is in engineering. “It’s a very odd feeling if you’re in the room when infrasound is present because it’s a sound that you feel rather than hear,” she says. “It’s like it gets in your body, you sense it almost like on your skin and you’re aware of it. If it’s loud enough, if it’s powerful enough, you have a sense of the air being alive in a certain way.”

Not that it’s a portal to the underworld. “If you’re expecting to see a dead uncle in the room or something like that, it wasn’t like that at all,” she says. “I mean, it’s a really marginal effect. It’s just like a slight addition to the room, a slight sense of something extra in the room. It’s almost like the room feels slightly electric.”

In 2003, Angliss and O’Keeffe collaborated on an experiment to test Tandy’s theory. “I started to realise that all these organ builders around the world have been building these pipes that are so long, and their bass frequency is in the infrasonic range,” says Angliss. These pipes were huge, and needed enormous bellows and engineering to force enough air through them to play a sound which nobody could actually hear. 

“So it begs the question, if this stuff is junk sound – stuff that we don’t need to think about because it’s outside the human range of hearing – why did people go to these extraordinary little lengths to build these pipes?”

They both went to St Albans cathedral to investigate. “It just didn’t make any sense why these pipes were being built. But when Sarah and myself were in St Albans cathedral, and we asked the organist to play an infrasonic pipe, you could feel an added intensity to the music. You could feel it in your body.”

Angliss felt it too. “These very, very deep pipes were put in to create that kick, some kick in the music, the drop, where you feel a sense of awe in the cathedral.”

She, along with the National Physical Laboratory, helped design and build an infrasound machine in a Sussex shed, using a 23-foot piece of corrugated plastic sewer pipe as their own organ pipe to create a resonance at 17.5 hertz. When they turned their ‘acoustic cannon’ on, odd things started happening: the strip lights in the shed vibrated and furniture trembled slightly. The room stayed nearly silent. 

Spookily enough, one of the best low-tech ways to tell the presence of infrasound is to light a candle and watch its flame flicker and tremble. “I used to go around and demonstrate it [the cannon] and [it was] very, very exciting to pick up a candle and just walk around the room and see the candle flickering as you moved into the antinodes of the signal, and bits of paper flapping, or the chair slightly vibrating, and you really felt it on your chest.”

Not everyone was keen on the experiment. Angliss remembers having “a whole stack of the email equivalent of green ink letters from physicists who said I shouldn’t be running the experiment on ethical grounds,” and had been warned off investigating infrasound by a salesman in an audio tech shop on Tottenham Court Road.

“He said, you really shouldn’t be messing with brown noise. It was like, ‘Don’t do drugs’ – like, you don’t know what you’re getting yourself into. It’s like the classic opening to a horror film. It was hilarious.”

Undeterred, says O’Keeffe, they “blasted infrasound at an unsuspecting audience in the Royal Festival Hall to test the theory”. On May 31 2003 they took the acoustic cannon to the Purcell Room at the Southbank Centre, where they put on two concerts on one afternoon that mixed live piano pieces and some of Angliss’ electronic work. Underneath the music, though, O’Keeffe mixed in sound from the cannon at different points in each performance. The audience filled out questionnaires detailing their feelings through the pieces.

“What was quite obvious,” says O’Keeffe, “was that people were having emotional responses to the music, of course, regardless of whether infrasound was present or not. Infrasound appeared to increase the intensity of the emotional response.”

It helped O’Keeffe and his colleagues come to the conclusion that Tandy’s idea was intriguing but imperfect. “Vic Tandy had a really interesting theory that I love, but actually his theory to say it was 19 hertz that was responsible for haunting experiences is not now held up amongst parapsychologists.”

Ghosts and poltergeists have a lot of causes, he says. “It’s a contributing factor, but we can’t say it is the cause of all haunting experiences.”

Many hauntings take place around bedtime or during the night, and “is easily attributable to the state between waking and sleeping, hypnagogic effects,” O’Keeffe says. The two biggest factors are psychology and the environment which a person is in.

“If you go into a place that I’ve suggested to you is haunted, and you feel a breeze on the back of your neck, potentially you’re going to be looking around thinking, was that a ghost that just walked behind me? As opposed to if you’re in an office building and feel a breeze on the back of your neck, and you’re looking for an open window or an air conditioning duct.”

A lab late at night, or a creepy medieval cellar, will prime a certain kind of response. “It affects your interpretation of what’s going on. So imagine in St. Albans Cathedral, feeling that physical effect of the infrasound and then interpreting it as a sense of profundity – a sense of awe here in the cathedral. Now, in a haunting context, given Vic Tandy’s theory, you experience the infrasound, you can’t attribute it to any source, it affects you physically and you think, well, maybe that’s the spirit, maybe there’s a ghost here.”

That gig in the Purcell Room suggested something similar. “It’s the same thing: people having an emotional response to the music, that response is not going to alter, but the intensity of the response will alter.”

Cox points out that infrasonic frequencies can penetrate most places you could try to hold an experiment: “It’s very hard to make very controlled experiments at these very low frequencies because any venues you go into are almost certainly going to be washed with infrasound from other sources.”

The other problem is that after a rush of funding when Defra tried to get to the bottom of annoyance from infrasound and ultrasound around the turn of the 2010s, few academics have returned to the subject. “There’s just not been very many experiments, to be honest,” says Cox.

Angliss, though, has applied infrasound in work including a production of The Twilight Zone at the Almeida, and she still feels the excitement of first exploring infrasound. “It was like opening an amazing door. Oh my god, I just could not believe what I found. There’s all these tantalising things.”

I want to feel these tantalising things too, so I open one of the many YouTube videos purporting to send out the 19 hertz ‘fear frequency’. A comment on one 12-hour video makes it sound particularly promising. ‘I am listening to it right now and well... as soon as I placed it [sic], the vains [sic] in my face starting pumping, as I am typing this, it’s a little hard to breathe, this stuff is pretty cool, I am starting to see things, my feet are vibrating. This is sick.”

I put my AirPods in and wait for something to happen. There’s a soft rustling noise, like static down a phone line. I sit in my kitchen waiting for a visitation for a good 15 minutes before admitting it’s not happening. No tingle on the back of the neck, no cold sweats, no ghosts. It turns out firing up a very compressed YouTube video on my tinny laptop speakers in a bright, tidyish flat at 8am doesn’t have quite the same presence and effect as a giant pipe organ in a creepy cellar in the dead of night. 

It doesn’t look like there are any ghosts in my machine. But there are still machines out there which might be sending infrasound silently into your home, shaking your eyeballs, and – just maybe – sending a shiver down your spine.